The subject matter herein relates generally to electrical connector assemblies, and more specifically to electrical connector assemblies that are configured to control impedance at a mating interface between the electrical connector assembly and a mating connector when both fully mated and only partially mated.
Some electrical systems, such as server systems and the like, utilize connector assemblies, such as header assemblies and receptacle assemblies, to interconnect circuit boards, such as a motherboard and daughtercard. The electrical systems may be relatively complex. For example, multiple connector assemblies mounted on a common circuit board may mate to corresponding mating connectors on different circuit boards. In addition, at least some of the circuit boards may be mounted to walls of a chassis, which fixes the circuit boards in place within the electrical system.
When the electrical system is assembled, the connector assemblies are mated to connect the different circuit boards. Two mating electrical connector assemblies are considered to be fully mated when signal and ground contacts of the first connector assembly engage corresponding signal and ground contacts of the second connector assembly and a mating surface of a housing of the first connector assembly abuts against a mating surface of a housing of the second connector assembly. The interface between the mating surfaces represents a mating interface. The signal and ground contacts extend across the mating interface.
Typically, at least some of the mating connector assemblies in electrical systems may not be able to fully mate when the electrical system is assembled and are only partially mated. Mating connector assemblies are considered to be partially mated to one another when the signal and ground contacts of the two connector assemblies are engaged but the mating surfaces of the housings do not abut against one another, resulting in an air gap at the mating interface. The air gap at the mating interface may be the result of various factors, including aggregated tolerances between components within the system, bowed circuit boards, imprecise assembly of the system, and the like. For example, if a circuit board is bowed instead of planar, a first connector mounted on the bowed circuit board may be able to fully mate to a corresponding mating connector on another circuit board, but a second connector adjacent to the first connector may be located farther away from the other circuit board than the first connector due to the curved circuit board. As a result, the second connector is only able to partially mate to a corresponding mating connector on the other circuit board.
Although partial mating of connector assemblies allows signal transmission across the connector assemblies, the air gap at the mating interface causes an impedance discontinuity, which may degrade signal quality and/or signal strength relative to fully-mated connector assemblies that lack an air gap at the mating interface (or at least have smaller air gaps at the mating interface). For example, the impedance discontinuity may cause some of the electrical energy along the signal path to reflect back to the source instead of being transmitted across the connector assemblies. The signal degradation caused by the impedance discontinuity at the mating interface may be exacerbated at high signal transmission speeds, such as speeds over 10 Gb/s.
A need remains for electrical connector assemblies with improved electrical performance (e.g., electrical signal transmission) at high speeds by improving impedance control at the mating interface regardless of whether mating connector assemblies are able to be fully mated or only partially mated.